Transparent Ultrafine Mineral Filler Technologies
January 2017 www.coatingsworld.com Coatings World | 49
contour plots, and Pareto charts. The response surface plots are useful to show
the correlation of the two factors ( 5 µm
N.S. and photoinitiator) with the response (t1/2). The contour plot is useful to
make predictions of the cure time based
on 5 µm N.S. and photoinitiator loading
levels. The Pareto chart determines the
importance of each factor in the response.
The response surface plots for the
DOE for each band (800-810 cm-1 and
1400-1410 cm-1) can be found in Figures
11a and b. A desirability of 1 is ideal,
as it represents the fastest, or lowest, cure
time for t1/2. The response plots show
a large correlation between the level of
photoinitiator and the cure rate, which is
expected. To a lesser degree, the amount
of 5 µm N.S. influences cure rate. For
each FTIR band, both surfaces are almost
identical, confirming that both represent
the same chemical conversion.
Contour plots for the response surfaces are shown in Figures 12a and b.
These plots predict the possibility of reduction in photoinitiator in combination
with the use of 5 µm N.S. For example,
at desirability of 0.5, or approximately a
t1/2 of 0.8 seconds, a loading level of 6%
solids of 5 µm N.S. could help reduce the
photoinitiator level by almost 20%. For
large scale production lines, this reduction could be substantial. To achieve the
fastest cure, the photoinitiator can be reduced by the same amount at a loading
level of 12% 5µm N.S.
The Pareto charts for each band can
be found in Figure 13. Pareto charts illustrate the importance of each factor being
studied. The standardized effect is the absolute value for that factor and includes
a reference line. Effects beyond this line
can be considered potentially important.
The level of photoinitiator is the most important factor; however, a loading level of
5 µm N.S. also has a significant effect on
the curing time.
Economic Considerations
with Synergistic Ultrafine
Nepheline Syenite
An important factor in the formulation of
commercial UV-cure coatings is the raw
material costs. One of the main benefits
of a natural mineral filler suitable for use
Photoinitiator (g or %) 5 µm N.S. (%) Half-Time (s) Stdev
1 1 0.549 0.047
0.625 6. 5 0.624 0.016
0.25 12 0.859 0.074
0.625 1 0.937 0.041
0.625 12 0.584 0.036
0.25 6. 5 1.027 0.052
0.25 1 1.326 0.098
1 12 0.447 0.033
1 6. 5 0.717 0.029
Table 5 - DOE and results from FTIR cure rate measurement for 800-815 cm-1 band.
Photoinitiator (g or %) 5 µm N.S. (%) Half-Time (s) Stdev
1 1 0.482 0.042
0.625 6. 5 0.545 0.010
0.25 12 0.751 0.070
0.625 1 0.833 0.008
0.625 12 0.539 0.014
0.25 6. 5 0.976 0.040
0.25 1 1.202 0.065
1 12 0.411 0.006
1 6. 5 0.616 0.014
Table 6 - DOE and results from FTIR cure rate measurement for 1400-1410 cm-1 band.
Figure 11. Response surface for DOE measurements at IR bands 810-815 cm-1 and 1400-1410 cm-1.
Figure 12. Contour plot of response surface showing the possibility of photoinitiator reduction from the
addition of 5 µm N.S. in the 800-810 cm-1 and 1400-1410 cm-1 regions. Faster curing is indicated by
higher desirability.
